Radio detection system for finding range and direction



pr 3, 1951 A. D. SMITH, JR., ETAL ,54705 RADIO DETEcTIoN SISTEM FOR FINDING RANGE AND DIRECTION Filed May 29, 1943 4 Sheets-Sheet l ATTRNEY April 3, 95 A. D. SMITH, JR., ETAL 2547,05E

RADIO DETECTION SYSTEM FOR FINDING RANGE AND DIRECTION Filed May 29, 1945 4 Sheets-Sheet 2 ATTORAH'Y April 3, 1951 A. D. SMITH, JR., ET AL RADIO DETECTION SYSTEM FOR FINDING RANGE AND DIRECTION Filed May 29, 1943 4 Sheets-Sheet 5 I N VEN TORS wy/@i515yr ATTHEY April 3, 1951 A D SMITH, JR. ET AL 2,547,053

RADIO D'ETCTION SYSTEM FOR FINDING RANGE AND DIRECTION Filed May 29, 1943 4 Sheets-Sheet 4 IN VEN TORS ATTORNEY Patented Apr. 3, 1951 UNiTfEfD S Application `May 29, 1943, 'Serial No. 488,976

21 Claims.

This invention relates :to radio detection sysitems auch :as used for detecting hostile aircraft and ships and for supplying fthe detected 'informationto predictors associated 'with gun emplacements.

It .is zone .of the objects of our invention to provide la radio .detection'system :capable of .being operated -easily and accurately by a .single ope ator.

iinother object 'of our invention is to provide a method and means for readily determining with a'l'ii'gh'degree .of accuracy the directionto and/or range 'of-La .detected craft :or other obstacle.

Another object-of our "invention Ais to .provide 'a Yscanning circuit for `cathode :ray oscillographs for use in :indio Y.detecting :systems and other electrical :circuits Vby which vthe focusing .and .other adjustment indications such as required "for vdetermination of elevation, fazimuth and ra'nge `of Va detected .obstacle Yare feasily observed and com- ;pared Awith a high degree .of accuracy.

Still .another object of the invention is 'to provide :a scanning circuit for cathode ray oscillographs capable of -.providing at least two spaced apart ytrace lines of predetermined character by which corresponding pulsations :on the lines may be 'easily r:compared as lto alignment and amplitude.

The above and other :objects of the invention will become more Aapparent :from .the iollowing detailed description and kthe appended 'claims read :in'connecticn with the accompanying `drawings, in which:

Fig. `1 :is la schematic block diagram of a radio .detection systeminzaccordance with ithe principles fof our invention;

Fig..2is.a schematic -.Wiring diagram .of apart-oi the Yscanning circuit for the oscillograph of the :system:

Fig.. 3 .is a :block diagram roi another `part of the scanning circuit ofthe oscillograph 'together with graphical illustrations of the scanning potential ,and fdeecting 4pulsations applied to one of the vdeilection circuits .of the oscillograph;

.'Fig. l'et is a :schematic illustration of the voscillograph screen with aiour sided tracing in which the :opposed pulsations, `while shown `in alignment, indicating .accurately `vthe range of the fobstacle'producing the pulsations, are ci ydifferent .amplitude and therefore "indicate that the system is improperly directed at the obstacle producing the pulsations;

Fig. 5 is a 'bloc-k diagram of a modified portion foi the scanning circuit for the ysystem shown Fin Fig. it

Fig. `6 is a graphical illustration -of vthe-operating steps of the 'elementsof l'ig. 5; and

Figs. 7 and -8 are lschematic illustrations Ao'f 'an oscillograph provided with iltracings in .accordancewith the scan-ning features of Figs. 5 and -6.

Referring to Fig. El, "the radio detection `system therein *shown includes a transmitter l@ having fan antenna `If2 whichis arranged to transmit "a :train of impulses such as theseries X1, X2, X3,`X4, letc. indicated by-curve "I5 '(Fig. -l`-) in accordance --with the operation of Ia synchronizer 1d. Relrad'iatable lobstacles such vas fa metallic `aircraft fl i' fw-ithin'fthe 'rangeof the -system will reflect the impulses as Aecho pulses EXI, TEX-2, etc. curve 15. `These echo pulses are received on yantenna e'lements 21, 22, '23 and "24 of a'direc'tional antenna 2). The directional antenna 2"!) 4may :comprise any suitable arrangement of elementswherethe radiation lobes are disposed Atwo lin a vertical plane, suc-h -a-s yrepresented 'by 'the positioning of Aantenna elements -2-I and l22, fand two 'in a horizontal plane, such as represented by the positionlingfoi'elements 2f-3 and '124. 'Tf desired, any antenna array giving the proper y'c'iistribution of lobes, vertically and horizontally, may be used. 'The transmitting antenna may leven 'be 'incorporated `in the array. i

The angular position 'of the vantenna 2l! is 'controlled in elevation by a motor 26 and inaz'imuth 'by a v-motor 21. The motor 26 is controlled manually by a motor control 'device 30 4having a Ymanual-ly adjustable control '3L The adjustment 4of the motor and `therefore the angular position of the antenna -20 in elevation is indicated by va 'suitable ydia-l `and 'index device Vas shown 'at '32. 'The angle of adjustment of the Aantenna 2li for azimuth is 'likewise Vperformed "by va control 'device 33E for the motor 21. 'The vcontrol 34 has a'manu'a'l- `ily 'adjustable control 35 and an indicating dial The energy received by antenna Aelements 2| and v22 "is transmitted over vleads `'lll and 'd2 to an alternate blocking or switch device 5. The

. energy received` by antennas 23 and "2li is likei943, are .synchronized with the transmission of infipu'l'ses bythe synchron'izer 1:2. The blocking devices each operate 'to pass alternately the energy `received `by Jthe two antennas connected therewith. That Yis to say, the antenna 2l "is 3 connected for reception through the device 45 of an impulse XI (curve I5) and echo pulses such as pulse EX! received in response to impulse X|, and then is blocked during the interval of reception for the next succeeding impulse X2 and corl Y responding trailing echo puises.

The impulse X2 and its echo pulses received by the antenna element- 22 during the interval that reception by antenna 2| is blocked are now passed by the device 45. This alternate blocking then repeats with passage of impulse X3 from antenna 2| and then impulse X4 from antenna 22, etc. The device 46 operates similarly permitting passage of received energy from antennas 23 and 24. The energy passed by device 46 is represented by impulses YI, Y2, Y3, Yli, etc. and their respective echo pulses EYI EY2, EY3, EY4, etc. (curve |5a). The corresponding impulses XI, YI; X2, Y2, etc. are in timed relation since the corresponding impulses are derived from energy of the same pulse transmitted at I2.

Following through the circuit with the pulse energy passed by the alternate blocking device 45, this energy is passed by a lead 48 to a receiver E2. The transmitted impulses Xi, X2, X3, X4 etc. and their respective echo pulses received by the elevation antennas 2| and 22 are detected and amplied by the receiver 52. In curve I5, we have shown for simplification, the reception of a single echo pulse reected by craft "I 1 in response to each of the transmitted impulses. The train of impulses and echo pulses received at the receiver 52 is applied to a pulse inverting and mixing device 53. The details of the circuit 53 which are shown in Fig. 2 will be described hereinafter. For the present, the general function of the device will be explained.

Synchronized with the transmission of impulses by connection 64 with the synchronizer |4 and passing through an adjustable delay device I is a square wave generator 56. The rectangular wave 51 produced by the generator 56 is applied to the device 53 and this rectangular wave is used to invert alternate pulses as indicated by wave 58 and then superimpose them on the rectangular wave 51 in the manner indicated by wave 59. The output wave 59 of the inverting and mixing device 53 is applied to a mixing device 60.

The mixing device 60 serves to replace alternate cycles of the Wave 59 with a cycle of a scanning wave 62. The wave 62 is of saw-tooth triangular form and is generated by a generator 63 synchronized through delay device IDU by the synchronizer I4. This mixing operation is controlled by a blocking wave generator 65 which produces two rectangular waves 66 and 61 the phases of which are 180 apart and the cycles of which are twice the duration of the cycles of the rectangular wave 59.

The mixing operation of the device 60 will be explained by reference to Fig. 3. The wave 59 is applied to a blocking tube which is biased by the potential of wave 66. The portion 66a of the curve operates to pass energy of the wave 59 While the portion 66h operates to block the wave 59. This results in an output for the tube 19 corresponding to wave 1 I. The waves 62 and 61 are applied to a second blocking tube-12 in a similar manner whereby an output wave 13 is produced in which alternate cycles of the scanning wave 62 appear. The waves 1I and 13 are combined by a coupling device thereby resulting in wave 16. It will be noted that the cycles of wave 16 now comprise as alternate cycles, a cycle of the wave 59 and a cycle of wave 62.

Referring back to Fig. 1, it will be observed that the pulse energy (pulses Yi, EYi, Y2, EYZ etc. curve Iic) at the output of the blocking device 46 for antennas 23 and 24 is applied over connection 8i to a receiver 82. Similarly as in the case oi receiver 52, the output of the receiver 82 is applied to a pulse inverting and mixing device 63 similar to the device 53, whereby an inversion of successive pulsationintervals is obtained (curve 58a) and the pulsations applied to a rectangular Wave as indicated by curve 59a by application to the device 83 of the rectangular wave 51 from the generator 56. 'I'he wave 59a is applied with the energy of the wave 62 to a mixing device 84 identical to the device 69 to which blocking energy from generator is applied. The device 84 has an output wave 16a which is similar to the wave 16 (Fig. 3) except that wave 16a is 180 out of phase therewith and the impulses appearing here are those received by the azimuth antennas 23 and 24. This phase relationship is readily observed from the aligned relationship of the two waves illustrated in Fig. l. This difference in phase is obtained by reversing the Wave energy 66 and 61 from that shown in Fig.V 3. That is to say, the wave 61 is used for blocking alternate cycles of the curve 59a while curve 66 is used for blocking alternate cycles of the wave 62.

The wave 16 is applied preferably across the vertical deflecting plates 9| and 92 while the wave 16a is applied across the horizontal plates 93 and 94. The scanning portion 62a of wave 16a controls the movement of the cathode ray beam between deflecting plates 93 and 94. During the movement of the beam from the left to the right of the screen 95, the portion 51a of Wave 16 controls the vertical deection of the beam. Thus, the potentials 62a and 51aV cause the beam to shift to point 95a and to travel therefrom as indicated by arrow 96 to 95h, thereby providing (in the absence of impulses XI, EXI etc.) a substantially straight trace between those two points. The drop in potential at the side between the first and second squares of the portion 51a causes the beam to shift instantly from point 95h to point 95c so that during the last half of the scanning potential 62a, the beam traces in the direction of arrow 91 a line between points 95C and 95d. At the end of the deflection porl tion 51a, the portion B2b of curve '16 controls the vertical scanning of the beam while portion 511) of curve 16a controls the horizontal deflection of the beam. Thus, as the potential 62h controls the scanning of the beam between the bottom and top side of the screen, the beam will be caused to first shift back to point e and then move as indicated by arrow 98 between points 95e and 95h and on the return movement of the beam between points 95a and 95d as indicated by arrow 99. It will be observed, therefore, that a substantially square tracing will be produced according to the wave forms of curves 16 and 16a.

At this point in the description, we want to make it clear that our system is not limited to a rectangular tracing but may produce in eiiect two trace lines spaced apart in accordance with any two of the parallel trace lines of the tracing illustrated. By this We mean that by applying.

the wave 51 across the vertical plates 9| and 92 and by applying the scanning Wave 62 across the horizontal plates 93 and 94, two tracings one between points 95a and 95h and the other beil'5 'points sie and :95d will be produced. parallel tracing eiect :be lelettr hereinafter, may he used for producing alignment between corresponding echo pulses i-or the purpose of ob- .Ltaining the range Aon the obstacle :producing such echo pulses. it will also be clear that by reversing 'the application :of the Waves `,E53 :and E2 with the elevation and `azimuth of .a detected obstacle,

`lthe .means `for `determining the `distance to the fobstacle `he described. :The delay 'device illil :in the synchronizing eireuift for vthe generators 56 :and 65 is .controlled b y device lill. 'The control device includes a dial and indicator .arrangement |02 by which the degree `of retardation =o energy passing through the device lill! indicated. The device l'lli may be controlled -hyahand control i103 .for byrneansaof a foot :pedal |04 connected thereto by cables 1:85 or by 'any .fother :suitable motion transmitting means. Assuming that the receivers 52 land .182 are 'conditioned to receive the .impulses .transmitted by the transmitter IB, the impulses vwill appear on che screen .95 Yas Xl, YS `and Ys. 'Ilo obtain .la izero 'distance indication .on the device lill., the delay dev-ice im] is :adiusted by manipulation zot the control 4i193 until each pair of transmitter pulsa-tions Xi, X2 .and 3.73 YA are `brought into alignment. vIt 4is preferable to lcontrol the amplif tude fof the pulsations by 4means of amplitud-e eon-trolsvZu. and-82o associated `-with receiyers 52 and 82 so that the peaks thereof willextend within .a centrally located `circular 'mark llt on the screen S5. It Will be understood `that mani-pula- `tion of the control 1&3 will cause the pulsations of each-.pair .(Xl, X2 and X3., YA) tto move in opposite directions .as indicated -hy .ar-rows 9S, -537 and 98, .99. By proper .manipulation it is patissible to :line up the opposed pulsations substantially .as indicated. This adjustment may :be

taken las the zero distance position for the eontrol. .It will ehe understood, of foon-rse, that :.is only necessary to fcheckfon the .zero distance indication of the .system-occasionally .for purposes of checking Y:the vcalibration of the dista-nce indicating dial .I-2.

Since Aeach Vimpulse is accompanied by an echo pulse, the -echo pulse EX! rollo-Wing .the pulsation v'Xl .is to .the right of Xi ion the 95 .while the .echo `pulse EX2 is to the left of pulsation X2. .By proper .manipulation of .the control 103, the pulsations XI Aand .EXI will he .shifted to the left and the pulsations X2 and EX will be .shifted .to the rightuntil the pulsations EXI .andEXZ .are in alignment. The adjustment hike- Wiseshifts the opposed pulsations EYS and into alignment. this condition is reached, the .adjustment of the control .as `indicated 1.on vthe dial 182 .give .the .distance to the aircraft ll. By proper adjustment .of controls 52a and 82a the amplitude ofthe lecho pulses can he increased until their .tips coincide, thereby giving a more accurate .setting than would he had were they left-small.

lll/'hen it is desirable to obtain indicationslo-f elevation `and .azimuth Iof the aircraft or .come other obstacle, it .may flac desirable -to .eliminate the pulsa-.tions Xl, `X2 and Ys, lYA from the screen. 'Ihis may he accomplished .by .a .blocking .circuit irom the .synchroniser il! or transmit- .pose ris .shown in the :copending application of Labin, .Serial No. MT1-1,228, led January 4., .1943, now Paten-tNo. 2,471,436, granted :May B1, 1.9.4.9.. The blocking potential of the Labin system comprises ;a `negative potential Vobtained `in .the generation of the impulse energy .for the transmitter. This 'negative potential .is then `expanded in time yso as to loverlap the vperiod of radiation .of the impulse. It j-is :this :negative potential that .fmay be .applied through .connection H2 to the .receivers 52 :and to vblock them during the :radiation Aof the impulses.

in place uol.D iblocking the impulses, their amplitudes .may be :limited so that :they will `not .extend more than hal-f -way across the screen r9.15..

Assuming that the antenna 2U\ is not properly .focused on the :aircraft Il, the amplitude 'of the Atwo pulsations .EXI .and vEXZ for elevation will not .be equal. .Such ,a condition is illustra-ted in Fig. 4. Thus, While the pulsations EXI :and EXZ will serve when inalignment as indicated in Fig. 14 for vthe ,purpose of obtaining the distance to the aircraft, .still other adjustments 'are necessary to y.obtain :an accurate indication :of elevation and azimuth. By proper manipulation of the lcontrol 32| for the elevation .motor Z, the antenna 2j@ Vmay be maneuvered .in a vertical plane until :the echo pulses received by the antennas 2l and 22 :are substantially equal. When `this condition is reached, the pulsations :and EX! 'will he substantially .equal in amplitude and the peaks thereof will extend Aclosely adjacent the center of the .circular mark :l lll. 'Such a condition is illustrated on the screen 95 of Fig. l forthe pulsations 1X1, X2, and YS, Yll. When this equal .amplitude `condition of the pulsations EX! and EXZ :is obtained, the elevation indication at v32 fgiyes the angle of elet/ation 'to the location of the .aircraft El 1..

Ihezadnstments for azimuth are similar to 'the adiustrnents for elevation. The control 3&5 is manipulated to shit'the antenna 2li soas to 'move the antennas 23 and 24 in a horizontal 4plane until they receive equal intensity :of the echo .As stated in connection vwith the .elevation adjustments, Awhen an equal amplitude .oondition is reached for pulsations .EVS and `EY4, the -dial'l indicationat 3ft Will .give the angle of azimuth tothe location :of aircraft l?. The location data .of distance, .elevation and azimuth vobtained and maintained accurate while the cra-it 4is in flight may 'he transmitted automatically over connec etions I-l5 'to predictor mechanism for gun ernplacements. Y

:the foregoing it will vbe clear that .a single may, Watching Ythe Vscreen 85 .of the snag-le oscillograiph, manipulate the three controls 31,35 and m3 with secondary adjustments off controls maand iaato .obtain accurate indications of selevatiomazimuth 1and distance to the location .or ythe :aircraft Il or any other obstacle detected AYby echo pulses .produced thereby. This -i's of .particular 'importance today where skilled operators .are in :such great demand.

It'will :also he .clear :that the system may be 'fused obtaining .distance only or for direction lind ing only. ln either case, the apparatus may :be simplified to include .only that porti-on .of the apparatus 'necessary to perform V'the function .desircd.

Referring bac-kite 2, .a l.detailec'l description yof pulse inverting nndrnixing .device E3 will :new be given. The train lol. pulses Xl, "X2, and 5X6 tourne H59 Adetected receiver 52 fis apli. Aisnitahle blocking .controlior plir- VV'plied 'to the .input 'lzll to :an ampliner 'tube 'VA-1 which acts as a coupling amplifier for the device. The anode output |2| reverses the pulses XI, X2, etc. to positive pulses as indicated at |22. The pulses of curve I5 are illustrated as negative but, of course, may be taken as positive, whichever adjustment is desired.

The energy according to the train of pulses |22 is applied to the control grid |23 of a vacuum tube V2 and to the control grid |25 of a vacuum tube V3. The tube V2 o-perates to invert the energy |22 applied thereto as shown at I 26. This inverted energy |26 is applied to the control grid |28 of a vacuum tube V4. As will be explained hereinafter, tubes V3 and V4 operate to block out alternate sections of the energy |22 and |26, respectively.

The rectangular Wave 51 produced by the generator 5t (Fig. l) is applied to the input |30 to the control grid of a tube V5. Each cycle of the wave 51 is formed of two rectangular portions Xa and Xb. This wave energy when obtained from the anode connection |3I of the tube V5 is inverted as indicated at |32. This energy is passed over connection |34 to a, grid of tube Vs. The portions Xb of the rectangular Wave will be positive on the cathode |35 of tube Vs. This positive portion Xb is applied to the cathode |36 of the tube V3 as a blocking potential so that alternate pulses such as the pulses X2 and the associated echo pulse EXE are eliminated from wave |22. This leaves the anode energy of the tube V3 substantially as indicated at |40. This anode energy is applied over connection I4| to an outlet connection |42.

The blocking potential for tube V4 is taken from the anode connection |34 of tube V5 by a connection |44. The connection |44 applies the wave energy |32 to the control grid of a vacuum tube V7. By taking the anode energy at |45, it will be seen at |46 that the wave is inverted so that the portion Xa is now positive. This wave energy |46 is applied to the control grid of a vacuum tube Va. The portion Xa of the Wave |46 is positive at the cathode |48 of the tube Vs and is applied over connection |50 to the cathode |52 of the tube V4 thereby blocking the tube V4 to those pulses occurring during the intervals covered by portions Xa of the wave |32.' Since portions Xa are in phase with the portions of the input Wave I5 at |20 in which XI and EXI occur, those pulses will be eliminated leaving pulses X2 and EXZ as indicated at |54. The anode output of tube V4 as indicated at |54 is applied to the outlet connection |42.

The rectangular wave |32 is also applied as indicated at |53 to the control grid of a vacuum tube V9. By taking the anode potential of the tube V9, the wave |32 will be inverted back to the phase relation of the input curve 5'! at |30, This anode energy is indicated at |59 and is applied to the output connection |42. The combining effect of the rectangular Wave |59 with the pulse energies |40 and |54 produces the iinal output wave 59. It will now be observed that the pulses X2, X4 have been inverted with respect to the pulses XI, X3 and the pulses XI, X2, X3 and X4 applied to the successive portions of the rectangular wave.

Referring to Figs. 5, 6, 7 and 8 of the drawings, we show a modification of the scanning potential for the oscillograph to be used in the system of Fig. 1. The block |56 replaces the wave generator 56 of Fig. l. The apparatus 'of this block diagram is arranged to produce a wave shape differing from the rectangular wave shape 51. by

a curvature which operates during the scanning periods to deect the tracing so as to produce inwardly or outwardly directed cusp portions, whichever may be desired as indicated in Figs. 7 and 8. The cusps of the scanning line extend the length of the tracing thereby enabling an operator to obtain a more accurate alignment of the pulses.

The block diagram |56 includes a square wave generator |60 and an oscillator |62 which are controlled by connection 64 from the synchronizer I4. Curve a of Fig. 6 represents a rectangular Wave I6| produced by' the generator I 60. The oscillator |62 produces a sinusoidal wave |63 or I63a of the phase relations indicated by curves b and d of Fig. 6. When the waves of curves a and b are mixed in mixer tube |64, a wave |10 substantially as indicated by curve c is produced. This wave includes alternate curved portions I1| and |12 the cusps of which extend toward the axis |14 of the Wave. When the Waves of curves a. and d are mixed a wave I1|Ja is produced substantially as shown by curve e.

The wave |10 or |10a, as the case may be, is used in the system of Fig. 1 in the same manner in which the rectangular wave 51 is used. As shown on the screen 05 in Fig. '7, the tracing |80 corresponding to Wave |10 is four sided in which each side |8I, |82, I 83 and I 34 curves inwardly toward the center of the screen. Likewise, curve 10a will produce a tracing |00 in which each s'ide I 9|, I 92, I 93 and |04 curves outwardly on the screen. By controlling the amplitude relationship of the Wave I 6I (curve a) and |63@ (curve d), the curvature of the sides may be varied from substantially rectangular to circular and further to a four lobe effect. The lobe eiect is indicated slightly in Fig. 8.

While we have shown and described the principles of our invention in connection with speciilc embodiments, we recognize that various changes and modifications may be made therein without departing from the invention. For eX- ample, the crests of the oppositely curved portions of the tracings of Figs. 7 and 8 may be arranged to extend in the same direction, especially Where only two spaced apart tracings are desired. The scanning intervals may also be increased with corresponding decrease in the ampli-A tude of the deiiection Wave 51 (Fig. l) or |6I (Fig. 6) and by proper control of the beam intensity show on the screen 05 only the central position of each side of the tracing. It is, therefore, our aim in the appended vclaims to cover all such'changes and modifications as fall Within the scope of our invention.

We claim:

1 A method of determining the distance to an obstacle indicated on the screen of a cathode ray oscillograph by echo pulses produced by the obstacle in response to transmitted impulses, comprising transmitting impulses, detecting echo pulses produced by said obstacle, producing at least two spaced apart trace liners on the oscilloscope screen, controlling the course of the respective traces by energy of the said impulses and of said echo pulses applied synchronously with the occurrence of the respective traces and with a respective mutually opposed polarity so that oppositely extending impulse and echo pulse indications are produced on the respective trace lines, retarding certain of the beam controlling energy until the impulse indications of the two lines are in alignment thereby obtaining a zero distance indication, and varying the retardation of the beam controlling' energy' until die opposed che pulsem indications' corresponding to the detectedv '.a'bstacleV are in alignment, vlheroyv the adjis`t= :nent df energyetardation from tlilzer'o indication clir'rslonds" t6v the distance t''said obstacle.

2". metrica dennen craint i wherein said twotracelines aremade'substantiailypar llel.

e'. The method dennen in einen i", wherein said t`wo`trac'elinesv are'cu'r'ved.

4. A method of determining the' location ci an obstacle' indicatedv on the screen of a catlioderay oscillogr'aph by echo` pulses' received by antenna' means including at least two spaced apart ai;u tnnas', comprising transmitting impulses; detecti'ng echo pulses producedV bythef obstacle, pio: vidi'ng scanning energy: toY control' the" beam' of the oscillograpli to produce across said' screen at' least two* spaced apart trace lines, effecting al; ternately' an indication on apli of the trace lines of corresponding echo pulses as received' by' the respective antennas; applying the'e'nergie's dueto' therespective pulses to produce' substantially juXt-apesedi indications, varying the'angul'ar rela: tionY of the antennasV andv substantial'lyy en 'uali'zing the amplitudev of the traces of the" juxtaposed' echo'pulse'scorresponding'tdjsaid obstacle, where: bythe positioning ofthe antennas'rep'resents oneA of theV direction components tothe" location of said obstacle method deiined inf claim l;v'vlieiein saldi two' trace lines a-re substantially* parallel and the" respective pulse energies areapplied `with mut`v` ually opposed polarit-yto-produ'ce indications disposed ini opposed directions;

6. The method defined in claim 4 wherein scanning energyv isprovided' of the' character to produce trace' lines. which are curved-'.-

7. A method of determing the location of an obstacle indicated on the screen` of a cathode ray oscillograph by means of echo pulses producedi ley's the obstacle in response to transmitted` impulses, comprising transmitting impulses, prc viding scanning energyY to control the cathode? ray' beam to" produce a four sided tracing on. screen oithejosciliograph; eachoi theitracf represent-ing agiven time interval for' trans; mission of` an impulse and the reception ofY e'clio" pulses for a givenrangeg receiving' certain of the echo pulses for elevation determination and re.- ceiving" certain other of the echo pulses for azimuth determination', applying the elevation echo pulses to said beam in synchronism with the scanning of two opposed sides ci the tracing to produce corresponding pulse indications thereon, and applying the azimuth echo pulses to said beam in synchronism with the scanning of the other two opposed sides of the tracing to produce corresponding pulse indications thereon, varying directivity of reception for elevation until the elevation echo pulse indications are of corresponding amplitude, and varying directivity of re- :option for azimuth until the azimuth echo pulse indications are of corresponding amplitude, whereupon the directivity adiustments represent ingles of elevation and azimuth to the location of aid obstacle.

8. The method donned in claim 7 in combina- ;ion with the step oi retarding the scanning energy until the opposed echo pulses oi the four dded tracing are in alignment, whereby such re- ;ardation adjustment corresponds to the distance o said obstacle.

9. A system for determining the distance to an bstacle comprising means for transmitting imulses, means to receive echo pulses produced by reection from t'le obstacle in response to transmitted impulses, an oscillograph, scanning meanstoappl'y scanning energy to the cathode ray beam or thel oscillographto produce across the screen ci said oscillcgraph atleast two trace lines, means tol inverti the impulse. and echo' pulse energy with respect to one another meansto apply alternately on the two traceulines,thefinvertedenergy corresponding to said impulses' and said echo pulses respectively, the indications on the two lines extending opposed directions, means to retard the scanning energy until the impulse indications on. the two linesare in alignment, thereby obtaining aperof distance indication, and said energy retardingmeans beingfurther adjustable to bring' opposed echo pulse indications corresponding to the detectedobstacle into'alignment, whereby the adjustment of said retardation:` means from zero indication corresponds to the distance to saidobstacle. y

LQ; Thesystem definedy in claim 9 wherein said scanning means includes` linear trace line generating means to produce the two lines spaced apa-rt in substantially parallel relationship ll. The system dei-ined in claim 9v wherei-nthe said scanning means includes means providing avoltage wave` having curved portions and meansv for generatingai tracing signal therefrom: in'- whichthe-crest of alter-nater curved portions are extended in opposite directions.

l2. Asystemffor determining the loca-tion'rofV an obstacle comprising means to1 transmit impulsesp ay pair ofdirection findingantennas,` areceiver,y

4 means to; alternately switch the antennas-in coni-- i chronized` with. saidswitchingmeans VVtoapply nection-with said receiver synchronism with transmission of impulses,4 an osci-llograph, scan-- ning.. means to produce` across the screenf of said oscillograph at least two trace. lines-,means-syn-- alternately pulse indications of the echov pulses. produced bysaid obstacle in 4response to-said-im pulses ii-rs'tV one ononeof said; linesandthe'next. to the' other of said lin`es,andV means to vary the angularY relation ofk said antennas until" the. opposed echo pulses are Vof substantially equal arri-- plitde",r whereupon" tl'ief ypo'sit'i'oningV of the: an,-V tennasrepresents one oi' the direction-components to thelocation oi said obstacle.l v Y Y 1'31 Thesfste'm denedihi claim` l'2` whereinftle twd antennas are arranged idr' rov'einen't in a vertical plane so" that" the directin' cdin'p'oriet obtained is the angle of elevation to the location of said obstacle.

i4. The system donned in claim l2 wherein the two antennas are arranged for movement in a horizontal plane so that the direction component obtained is the angle of azimuth to the location of said obstacle.

l5. The system defined in claim l2 wherein the scanning means is arranged to produce the two lines spaced apart in substantially parallel relationship.

16. The system defined in claim l2 wherein the scanning means includes means providing a voltage wave having curved portions in which the crest of alternate curved portions are extended in opposite directions.

17. A system for determining the location of an obstacle comprising means to transmit impulses, receiver means having a directional antenna, an oscillograph, means to provide scanning energy to produce a four sided tracing on the screen of the oscillograph, each side of the tracing representing a given time interval for transmission of an impulse and the reception of echo pulses in 1l response thereto for a given range, control means to adjust the directional antenna for reception of certain of the echo pulses for elevation determination and to adjust the antenna for reception of other of the echo pulses for Aazimuth determination, means to apply the elevation echo pulses to the oscillograph for location of corresponding pulse indications on two opposed sides of the tracing, means to apply the azimuth echo pulses to the oscillograph for location of corresponding pulse indications on the other two opposed sides of the tracing, said antenna control means being adjustable until the elevation echo pulse indications are of substantially equal amplitude and the azimuth echo pulse indications are of substantially equal amplitude, whereupon the directivity adjustments thereof represent angles of elevation and azimuth to the location of said obstacle.

18. The system defined in claim 17, in combination with means for retarding the scanning energy until the opposed echo pulses of the four sided tracing are in alignment, whereby the retardation adjustment corresponds to the distance to said obstacle.

19. A radio detection system having means to transmit impulses, a directional antenna, receiver means coupled with said antenna to detect (as to angles of elevation and azimuth) echo pulse reflections produced by an obstacle in response to said impulses, control means for adjusting the antenna in angles of elevation and azimuth, a cathode ray `oscillograph, scanning means including adjustable delay means for retarding the scanning energy thereof, means to apply to said oscillograph energy of said impulses and echo pulses to produce separate indications on the oscillograph screen, means to operatively relate the amplitude of the pulse indications to the directive angles of elevation and azimuth as determined by the position of the antenna, and meansl to vary the mutual pulse indication positions according to the distance of the reflecting object, whereby one operator is capable by observing the screen of the oscillograph to manipulate said con@ trol means for determination of angles of elevation and azimuth and to manipulate said adjustable delay means to obtain the range of the detected obstacle.

20. A visual indicator for simultaneously selecting preferred values of three variable quantities, comprising means for displaying four linear marksin two, parallel pairs, means to vary the relative lengths of the marks in one pair in response to changes in the value of one of said variable quantities, means to vary the relative lengths of the marks in the other pair in response to changes in the value of a second of said variable quantities, and means to move the marks of either pair in the direction perpendicular to their lengths in response to changes in the value of the third of said variable quantities.

21. An arrangement for .determining the range, azimuth andy elevation of an object, comprising a source of electromagetic waves, means to transmit waves from said source to the object, directionally selective means for receiving echo Waves from the object in response to the transmitted waves, means to adjust the direction of pointing of said directionally selective means, an oscilloscope, means to display upon the screen of said oscilloscope a plurality of elongated marks the relative lengths of which indicate a departure of the direction of pointing of said directionally selective means from the direction of the object, a range measuring device controlled by echo Waves from said object and having a range scale, said range measuring device comprising means to vary the range scale reading and simultaneously to vary the positions of said marks relative to one another to indicate a departure of the scale reading of the said range measuring device from the correct reading corresponding to the range of the object.

ARCHIBALD D. SMITH, JR. HORACE M. GUTl-IMAN.

- REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,924,174 Wolf Aug. 29, 1933 2,127,415 Marique Aug. 16, 1938 2,189,549 Hershberger Feb. 6, 1940 2,275,460 Page Mar. l0, 1942 2,312,761 Hershberger Mar. 2, 1943 2,406,358 Doba Aug. 27, 1946 FOREGNV PATENTS Number Country Date 552,072 Great Britain Mar. 22, 194.3 

